enter image description here

Look at these two photos of my shadow from sunlight.

Case 1: My shadow is separated from the shadow of the ceiling and my head is round.

Case 2: But when I walk a little more and the shadow of my head and the shadow of the ceiling are almost together, the shadow of my head tends to deform. Why?

Edit: Ok. The deformation is because the sun is not a point source and there are fuzzy shadows. But when I look the second picture only my head is deformed and not the ceiling, why?

Here is another picture.

enter image description here

  • $\begingroup$ I am wondering if diffraction has any role to play here. $\endgroup$ – Yashas Feb 17 '16 at 7:04
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    $\begingroup$ Related: physics.stackexchange.com/q/94235/2451 and links therein. $\endgroup$ – Qmechanic Feb 17 '16 at 7:09
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    $\begingroup$ @Qmechanic: Not only related, but virtually a duplicate, right? $\endgroup$ – pela Feb 17 '16 at 7:35
  • $\begingroup$ @pela: Yes. Btw, you yourself can vote to close as a duplicate. $\endgroup$ – Qmechanic Feb 17 '16 at 11:35
  • $\begingroup$ @Qmechanic: Thanks, I just didn't have the time to read through the whole answer at that time, and when you, the author, didn't say it was a dupe, I wasn't sure. $\endgroup$ – pela Feb 17 '16 at 12:34

I have notices this too. If you look carefully, your shadow is not sharp at boundaries. The boundaries has a thin band of light shadow which when you look individually is not easily noticeable. When two shadows come close, the light band of two shadows combine to form darker shadow and it looks like one of the shadows is deforming, or extending.

You see your shadow deforming because rest of the boundary of ceiling has only its own shadow. Where the two meet, only that place the two light bands combine and cause darker shadow giving an impression that your head shadow is deforming.

The thin lighter band is due to bending around the corners, do not recall what the name of phenomenon is, may be diffraction.

When the two shadows come closer, the two objects (you and the ceiling) are actually blocking light path , there is no boundary and diffraction does not take place at that location.

  • $\begingroup$ thanks. But why the shadow of the ceiling is not deformed? compared with my head, my head has a big deformation $\endgroup$ – Julian Feb 18 '16 at 6:39
  • $\begingroup$ Shadow of both deforms (or of neither). We see the head shadow deforming because the deformation is only happening at the approach point, which is significant for the head, but very small for the ceiling. Outside the ceiling shadow, we see the deformation and our eyes relate it easily to the head shadow deformation instead of both. Also, as it happens as a result of head shadow movement, mind relates it to head shadow, rather than ceiling shadow. $\endgroup$ – kpv Feb 18 '16 at 7:16
  • $\begingroup$ As it happens due to the movement of head shadow, it also moves with it and so we think it is part of head shadow (because it is moving with it). Ceiling shadow is not moving. If you move the ceiling, then you might see ceiling shadow deforming. Deformation appears to be part of the shadow that is moving. $\endgroup$ – kpv Feb 18 '16 at 7:20

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